duncan



3 Sheets-Sheet 1.

L. DUNCAN.

I ELECTRIC MOTOR.

Patented May 6, 1890.

(No Model.)

- (No Model.) 3 Sheets-Sheet 2. L DUNCAN ELECTRIC MOTOR.

o. 427,503. Patented May 6, 1890.

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L. DUNCAN.

ELECTRIC] MOTOR.

No. 427,503. Patented May 6, 1890.

UNITED STATES PATENT OFFICE.

LOUIS DUNCAN, OF BALTIMORE, MARYLAND, ASSIGNOR OF ONE-HALF TO HIRAM H. CARPENTER, OF NEXV YORK, N. Y.

ELECTRIC MOTOR.

SPECIFICATION forming part of Letters Patent No. 427,503, dated May 6, 1890.

Application filed January 2, 1889. Serial No. 335,816. (No model.)

T at whom it may concern;

Be it known that I, LOUIS DUNCAN, a citizen of the United States of America, residing at Baltimore city, in the State of Maryland,

have invented certain new and useful Improvements in Electric Motors, of which the following is a specification, reference being had therein to the accompanying drawings.

My invention relates to electric motors, and

re has for its object a construction which shall be of relatively small weight and great efficiency, wherein the revoluble parts shall move ata low rate of speed, thereby dispensing with the intermediate gearing or belting r 5 which is necessary where slowly-moving machinery is driven by ordinary motors, and also wherein the resultants of the moving forces are evenly distributed throughout the revoluble parts.

:0 Referring to the accompanying drawings,

wherein the same indicating letters and numerals refer to thesame parts on each figure, Figure 1 represents a view in perspective of the motor proper, a portion being broken 2 5 away to show the internal arrangement of the parts. Fig. 2 is a cross-section on the line 00 a; of Fig. 1, showing also a section of the polar projections on one side of the motor only. Fig. 3 is a view in perspective of a portion of the armature, showing the method of winding the same. Fig. i is a similar View showing the method of winding the field, also showing in cross-section two opposite and adjacent polar projections on each 3 5 side of the motor. Fig. 5 is a view showing the armature partly in perspective, with only four coils of the thirty coils which are shown in Fig. 2, the remaining twenty six coils being omitted, as they are not necessary to a proper understanding of the figure. This also shows a plan 'view of a portion of the commutator with four groups of the segments thereon, the remaining segments, numbering three hundred and sixty, being equally distributed around the face of the commutator and are omitted in the drawings, as they are not necessary for the proper understanding of this figure. This figure shows a form of commutator differing from that shown in Fig. 1, and which may be used with the peculiar field-magnet and armature of this motor.

A represents the shaft of the motor; IS,

the field-magnets, which consist of the part a, extending from side to side of the motor,

and the parts bl), which I herein dcnominate polar projections, those on the one side being further marked N, those on the other being marked S, and the insulated wire 0 comprising the winding of the field.

0 represents the armature; (Z d, the windings of the same. Said armature is centered on the field through the spokes a and the sleeve m.

D shows one form of the commutator, and c e c 6 represent the intermeshing gearwheels by which the brushes ff are rotated upon it. The rings 9 g, upon which the brushes also bear, are connected with the opposite poles of the source of electrical energy.

In the form shown the field-magnets are made of metal capable of magnetic induction, preferably of wrought-iron, and consist of the cylindrical portion a, shrunk upon the shaft A, and of the polar projectionsb 1), fastened securely to the part a, bent at the upper part, so that their inner surfaces form right angles inclosing the armature O, and so arranged that the ends of the projections on the one side are midway between the projections on the other side.

In the drawings a motor having twentyeight polar project-ions, fourteen on each side, is shown. The field-windings are divided into two coils for convenience, and are so connected as to magnetize the field-magnets in the same direction. They may be energized by the current flowing through the armature, or they may be connected in shunt relation to the armature or. otherwise in accordance with methods in common use. I do not confine my- 0 self to this particular form of field and winding, for under some circumstances it might be better that the section of the armature having the greatest length should be perpendicular to the motor-shaft instead of parallel, 5 as shown, and in this case the polar projections need not be returned over the armature, but could be straight and still present a considerable surface to the armature.

The essential feature of the field-magnets, which form a part of my invention, is that the polar projections of one electrical polarity on the one side shall be opposite the spaces between those of opposite polarity on the other side and that they be fewer by some 10; even number than the coils on the armature, for a purpose hereinafter fully described.

In the form of motor delineated in the drawings the field is revoluble and attached to the motor-shaft A, which it drives, while the armature O is stationary, being hold fast by the lugs L L, as shown in Fig. 1; but the field may be held stationary and the armature revoluble and attached to the shaft A, and the motor still would combine the essential features of my invention, which is appli cable equally to either method of driving the motor-shaft A. It is unnecessary to state that in the latter modification it would be convenient to alter the form of the field-magnet and armature.

The armature C is a ring similar in form to thewell-known Pacinotti or Gramme ring, but differing essentially as to the method of winding. As I construct itin'a motor having twenty-eight polar projections it has thirty coils d d surrounding it, the adjacent coils being wound in opposite directions instead of all being in the same direction, as in a Gramme ring. This is clearly shown in Fig. 3, there being a wire taken from the junction of the adjacent coils (Z (Z to one bar of athirt-y-part commutator, as in the ordinary Gramme armature.

The commutator may be stationary, as shown in Fig. 1, D, or revoluble, as shown in Fig. 5, D. In the stationary form (shown by D in Fig. 1) the two brushes f f are con nected with the positive and negative poles, re-

spectively, of the source of electrical energy through the stationary rings 9 g, upon which they bear. The brush-holder is revoluble, its motion being imparted from the rotating magnets through the train of gears e c e e, which is so proportioned that the brushes make fourteen revolutions for every revolution of the magnets and in opposite direction, for the purposehereinafter explained.

In the form of commutator D (shown in Fig. 5) the commutator is revoluble and has four hundred and twenty (420) segments, forming the commutator-bars, divided into twenty-eight (28) groups of fifteen (15) segments each. It will be observed that there are one-half as many segments on the commutator D as results from the multiplication of the number of polar projections by the nu mberof coils on thearmature. The brushes f f are connected with the positive and n egative poles, respectively, of the source of electrical energy. The turning of the commutator D coincides with that of the motor-shaft A. As before stated, but four of the groups of commutator-segments are shown in the figure and but four of the coils upon the armature. The path of the current is as follows: It enters the commutator by the brush f, passes from thence to the segment of the commutator immediately beneath it, thence in the direction of the arrow along the connectingwire to the dividing connection between the coils d d of the armature, thence, dividing the current, passes through the coils d and (1, (shown at the left of the figure,) thence simultan eously through the other coils 011 each side of the armature around to the coils (Z d on the right of the figure, and thence, coming together at the divided connection between the lastmcntioned coils, it follows the direction of the arrows back to the bar of the commutatorimm ediately under the brush f through which it reaches the source of energy. hen the brushes are upon these segments, all the teeth of the armature are energized excepting those between the coils (l (7 (Shown on both sides of the armature.) These portions, by reason of the direction of the current and the windings of the coils, are consequent poles, and thereforenot energized. The connections of the brushes are so arranged that when the current enters the coils (Z d the teeth between those coils are exactly opposite the polar projections of the field-magnet. \Vhen the commutator has moved through one four-hundredand-twentieth of a revolution, the teeth between the succeeding coils will be exactly opposite the succeeding polar projections, and as at the same instant the brushes pass upon the succeeding segments of the commutator,

and as these segments are divided into groups of fifteen (15) each, and as it is provided that all the segments of each group shall send the current in the same direction, and also that each succeeding group of segments shall change the direction of the current, it is evident that there will be twenty-eight (28) changes of the current at each revolution of the commutatora number corresponding to the number of polar projections in the fieldmagnet.

The operation of the motor may now be clearly understood by referring to Fig. 2. Here a section of the armature is shown, together with a cross-section of one set of the polar projections, which are marked N, these bein g all of the same polarity. As there are two less of the polar projections than of the coils (Z d of the armature C, then if one of these polar projections, (to which indicating-numerals are added in this figure,) No. 1, is directly opposite one of the armature-teeth, (which teeth are also numerically distinguished in this figure, Nos. 1' to 30, inclusive,) No. 1, then polar projection No. 15 will be opposite the armature-tooth No. 16. The portion of the armature between the coils d d I herein denominate teeth.

In the position above described, when proj ection No. 1 is opposite tooth No. 1 and projection No. 15 is opposite tooth No. 10, one of the brushes should be on that segment of the commutator connected with the coils on either side of tooth No. 1 and the other brush should be on that segment of the commutator connected with the coils on either side of tooth No. 16. The path of the current is from the battery or dynamo to one of the rings g (see Fig. 1) and through the brush to the segment of the commutator connected with the coils adjacent to tooth No. 1, or, if a revoluble commutator is used, such as is shown in Fig. 5, then the path of the current is ITO through the segment of the commutator from the brush f by the wire-connection to said tooth No. 1, and in both forms of commutator. Then, dividing, one half goes through the coils to the right of that tooth and the other half through those coils to its left, the two halves uniting after flowing through the coils adjacent to tooth No. 16, thence passing onto the other brush to the ring g and to the source of electrical energy, where the com mutator is stationary, as shown in Fig. 1; but where the commutator is revol'uble, as shown in Fig. 5, the current passes from tooth No. 16 to a segment of the commutator then im mediately in contact with the brush f and thence back to the source of energy. Under these circumstances the tooth No. 1 will be a consequent pole, Nos. 2 and 30 being of opposite polarity, and the same will be true of No. 16. The location of teeth Nos. 1 and 16 are indicated upon Fig. 2 by the inwardlypointing arrows. The distribution of polarity among the remaining teeth will be as indicated thereon by the letters N and S in Fig. 2. If the polar projections are of positive polarity, the direction will be opposite to that of the hands of a watch. When the motor has passed through a portion of a revolution equal to one twenty-eighth of a revolution less one-thirtieth of a revolution that is to say, through one four-hundred-and-twentieth part of one revolutionthe polar proj eetion No. 28 (between teeth Nos. 1 and 27) will come opposite the tooth No. 30, and projection No. 1% will be opposite tooth No. 15. The condition of affairs will now be exactly as before, for in either form of commutator the brushes are on the segment of the commutator corresponding with and connected to teeth No. 15 and No. 30, they having gone through one-thirtieth of a revolution in the form of commutator shown in Fig. l, and the commutator having moved through one fourhun dred-and-twentieth of a revolution in the form shown in Fig. 5, and the next succeeding segment has been brought under the brushes.

Itis evident that in the case of a stationary commutator with revoluble brushes, such as is shown in Fig. 1, the brushes move through one-thirtieth of a revolution, while the fieldmagnets move through one four-hundred-andtwentieth of a revolution, for the brushes move fourteen times faster than the magnets, this multiple of the rate of speed be ing effectuated by means of the gear-wheels e e c" 6'. Such a commutator would have but thirty segments; or it, as shown in Fig. 5, the commutator is revoluble and the brushes stationary, the current is brought into the coils on the armature at the instant of apposition of the coils and the polar proj ections by providing such commutator with twenty-eight (28) groups of segments, with fifteen (15) segments in each group, and revolving the commutator at a rate of speed coincident with that of the motor-shaft A.

I do not confine myself to any particular form of commutator, only requiring the essential feature that the brushes shall be on the commutator-segments corresponding to the teeth which are at that instant exactly 0pposite the polar projections.

Having thus described my invention, what I claim, and desire to secure by Letters Patent, is

1. In an electric motor, the field-magnet B, havi n polar projections I) b on opposite sides, those upon the one side being of one polarity and those upon the other side being of opposite polarity, arranged so that those upon the one side shall be opposite to the spaces between those upon the opposite side, in combination with the armature C, having a number of coils wound thereon, each adjacent coil being wound in an opposite direction, and the number of said coils greater by some even number than the number of said polar projections, as and for the purpose intended, substantially as described.

2. In an electric motor, the combination of the Field-magnet B, having polar projections l) Z) of opposite magnetic polarity, the armature O,havinga number of coils wound thereon, each adjacent coil being wound in an opposite direction, and the number of said coils being greater by some even number than the number of said polar projections, and the revoluble commutator D, composed of the following parts, to wit: the brushes f f, connected with the source of electrical energy and bearing upon the face of the commutator, the segments of the revoluble part being of a number equal to that number which results from the multiplication of the polar projections by the number of coils on the armature divided by the difference between the number of such coils and the number of such polar projections, the succeeding segments being connected with succeeding coils upon the armature, as and for the purpose intended, substantially as described.

3. In an electric motor, the combination of the herein-described field-magnet B, with its opposite polar projections bl), the herein-described armature O and its adjacent oppositely-wound coils (Z d, and the herein-described comn'iutating device so arranged and connected with said coils that the brushes f f will. always be upon these segments of the commutator which are connected with those coils upon the armature inclosing the teeth which are at that instant exactly opposite the polar projections of the said field-magnet, as and for the purpose intended, substantially as described.

In testimony whereof I aflix my signature in presence of two witnesses.

LOUIS DUNCAN.

\Vitncsses:

H. H. CARPENTER, JASPER M. BERRY, Jr.

ICC. 

